It is beneficial for a method or apparatus used for the detection of pathogenic microorganisms to have the ability to quickly provide an accurate result as to the presence or absence of the microorganism in a sample. This is true for those methods and apparati used to detect bacterial agents. Portability of a detection apparatus, enabling its use in the field, is also beneficial. Many prior art methods for detecting microorganisms have involved a significant lag time between sampling and detection and have employed techniques that are not readily adapted to portable devices.
Standard microbiological methods for detecting microorganisms have relied on substrate-based assays to test for the presence of specific bacterial pathogens. Such methods typically require growing cultures of the targeted organism, which can take twenty-four hours or longer.
Alternatives to standard microbiological methods include the use of antibodies and molecular detection methods. In many such methods, antibodies are used to first trap and then separate targeted organisms from other constituents in biological mixtures. Once isolated, the captured organism can be concentrated and detected by a variety of different techniques that do not require cultivating the biological analyte.
Previously disclosed methods for detecting analyte include ELISA, dot blot assay, electrochemiluminescence, flow cytometry, and matrix-assisted laser desorption/ionization (MALDI) time-of-flight (TOF) mass spectrometry (MS).
‘Polymerase Chain Reaction’ (PCR)-based methods have also been used to detect specific microorganisms in a sample. Such methods typically involve extraction of the genetic material (RNA and/or DNA) from a sample, amplification of a target genetic sequence specific to the microorganism of interest, and detection of amplification products.
Methods involving the use of bacteriophage to detect bacteria of interest in a sample have also been described. Some methods employing bacteriophage have relied on detection of bacterial components released from lysed bacteria following infection, while others have relied on detection of progeny bacteriophage or biological substances associated therewith. Genetically modified bacteriophage have also been described for use in methods of bacterial detection.
Most previously disclosed bacteriophage-based schemes for the detection of bacteria require bacteriophage replication and are, accordingly, associated with a significant lag time to detection. Additionally, many previously disclosed methods for detecting microorganisms are not readily adapted for use in portable detection devices. Methods for more quickly and accurately detecting pathogenic bacteria in samples, and portable devices compatible with such methods that enable detection in the field, are highly desirable.